Control systems



Jan. 27, 1959 J. F. SHANNON ETA.

CONTROL SYSTEMS Filed Jan. 1o, 1952 3 Sheets-Sheet 1 19.1.27, 1959...'F. '...HANNQN E. 2,810,729

*CONTROL SYSTEMS 3 Sheets-Sheet 2 yFiieol Jan. 10, 1952 5 Sheets-Sheet 3HH IHII J. F. SHANNON ET AL CONTROL SYSTEMS m .mi

Filed Jan. l0, 1952 m SNAM RONIA mNRH NAC NABS w.. EH n V H Ns o M1:..W-D

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ILLIM- l Unite States Patent O CONTROL SYSTEMS Jack F. Shannon, Euclid,vClayton H. Barnard, South Euclid, and Howard C. Schink, ClevelandHeights, Ohio, assignors to Bailey Meter Company, a corporation ofDelaware Application January 10, 1952, Serial No. 265,897 l 8 Claims.(Cl. 114-16) This invention relates to control systems and apparatus forsteam-powered submarine propulsion plants equipped with boilers havingpressurized furnaces. Oil is the fuel to be burned preferably, althoughany fuel burned insuspension, such as gas or pulverzed coal mightequally as well be utilized with our invention. Under surface andsnorkel operating conditions, air for combustion is to be furnished bymeans of centrifugal compressors, while under submerged operation,liquid oxygen will be pressurized, heated to normal temperature,vaporized under pressure and supplied to the furnace for combustion.

It will be understood that a snorkel is a breathing device used by asubmarine andmay include a tube or a pair of tubes housing air intake aswell as air and gas exhaust pipes that can be extended above the surfaceof the water for allowing operation with furnace or engine when thesubmarine issubmerged. The arrangement allows discharge of exhaust airand gases at all times without entry of water when waves submerge thej35exhaust port. The inlet port allows air entrance when not covered by awave but closes against water entry when the port is submerged by awave.

When using gaseous oxygen for supporting combustion exit products ofcombustion will be recirculated to dilute the gaseous oxygen and thuslimit furnace temperature.

During submerged operation, furnace pressure is necessarily held highenough to permit the exit gases to be discharged overboard against thesubmergence pressure then existing.

A principal object of our present invention is to provide method andapparatus for controlling the operation of such a steam generating plantoperating under surface, snorkel, or submerged conditions.

Another object is to provide an automatic control system of the fluidpressure actuated type for steampowered submarine propulsion plant.

Other objects will become evident from a study of the drawing and of thedescription thereof as well as the claims appended hereto.

In the drawings:

Fig. l is a diagrammatic showing of a steam-powered submarine propulsionplant to which our invention has been applied.

' Fig. 2 is a schematic showing of the measuring and controllinginstrumentalities of Fig. 1.

Figs. 3 and 3A illustrate a submarine, in side elevation, with a portionof the hull broken awayto disclose a diagrammatic showing of the vaporgenerator, propulsion equiment, auxiliaries, control panel, andprincipal interconnecting piping. i

The showing of the drawing is quite diagrammatic and not to any scale.The same numbers are used to designatek like parts on the sheets.

A pressurized boiler furnace 1 is shown as being supplied with fuel oilthrough a conduit 2, by means vof a pump 3 which is driven by a constantspeed electric motor 4. Regulation of the rate of supply of fuel oil ishad through the agency of a diaphragm actuated control valve 5 locatedin the conduit 2; while its rate of ow is continuously measured by aflow meter 6.

Air to support combustion is supplied to the furnace 1 by way of aconduit 7 to which is connected a cruising compressor 8 driven (whenoperating) by a constant speed electric motor 9. Also connected to theair supply conduit 7 is a main compressor 10 which is driven by anexhaust gas expander 11 and a steam turbine 12. When the main compressor10 is in operation approximately 30 percent of its driving power issupplied by the expander 11 and the remaining 70 percent by the steamturbine 12.

Under certain conditions of operation, to vbe explained hereinafter,oxygen to support combustion is supplied to the furnace 1 through aconduit 13 by an oxygen pump 14 driven by a variable speed driveelectric motor 15. The showing is quite diagrammatic and omits theequipmentl for gasification of liquid oxygen and two stages of gaseousoxygen pressure control. -The rate of gaseous oxygen supplied to thefurnace through the conduit 13 is measured by an oxygen rate of flowmeter 16 and is controlled by a diaphragm actuated control valve 17located in the conduit 13.

Under certain conditions of operation all of the exhaust products ofcombustion from the furnace 1 pass through a conduit 20 to the expander11 whereas, under other conditions of operation, a portion of theproducts of combustion are diverted through a branch conduit 21 whichjoins the oxygen supply conduit 13 on the furnace side of the oxygenregulating valve 1 7.

A separation drum 22 is connected to the Huid circuits of the boiler 1and is supplied with feed water through a conduit 23 by means of a feedwater pump 24 driven by a motor 25. Feed water supply rate through theconduit 23 is under the control of a diaphragm actuated valve 26 whilethe rate of water ow through the conduit 23 is continuously measured bya rate of ow meter 27. A water level measuring device 28 is continuouslysensitive to liquid level within the drum 22 for a purpose to beexplained hereinafter.l

Superheated steam leaves the boiler 1 through a conduit 30 whichbranches as at 31 to supply the steam turbine 12 when it is operating.The principal output of the power system, namely superheated steam,leaves through a conduit 32 and is measured by a rate of ow meter 33.The conduit 32 supplies superheated steam to one or more mainpropulsionturbines 110.

There are certain basic requirements to be met in the operation of sucha power plant. The rate of combustion must be controlled to satisfysteam demand. Fuel should be proportioned to oxidant when using airduring surface or snorkel operation, or when using oxygen duringsubmergence. A proportioningcontrol is provided capable of supplyingsufficient oxygen for eflicient combustion of the fuel oil. Contol offeed water supply will proportion the water inow in accordance withrequirements, and a spill-over valve from the drum to the main`condenser provides against excessively high drum levels duringmaneuvering or rapid start operations. When using gaseous oxygen forcombustion, exit gases will be recirculated to limit furnacetemperature. During submerged operation, furnace pressure will bemaintained high enough to permit the exit gases to be dischargedoverboard against the submergence pressure then vexisting. n

The boiler plant will function under threel phases of operation;surface, snorkel and submerged. The rst two modes of operation willutilize air from either the cruising or the main compressor, dependingupon load requirements. During submerged operation, liquid oxy- PatentedJan. 27, l1959 i asap-,pee

ee will be evaneretesiaiiri `suppl iesi to the `iii gaseous form. l

Surface operation- Light load The cruising cor npresser` 8 willbeusedjtosupply' air forl, `combustion during lperiods ofv light loadoperation.Since this unitis driven by a constant speed dirtcurrent motor 9i,control oftheamount. of combustion, air supplied is obtainedbythrottling a compressor spill-over valve 3 5 which wastes (tothe hull),vthe;air no t required for combustion. CQIltQl ofk thequantity of thefuel oil fired is accomplished by adiustinaa Strekeeperaier-On pump 3.and regulating one .or more burner, control valves A steam pressure,measuring-transmitter including Bourdon tube T26` and pneumatic pilotvalve 37 measures steam pressure inthe superheater outlet header 3i)yand d eyelops a proportional air pressure `signal in pipe 3 8 joiningtheA chamber of an ambient pressurecut-back relay 39 which may be of thegeneral type described and claimedin Dickey Patent 2,098,913. The outputpreSSllIe of relay` 39, availablein chamber D, is subjected throughapipe l0-upon the A chamber o f a ratiostandardizing relay 41 which isof the type described and claimed in Gerrie Re. 21,804. Relay 41provides a lproportional control with reset characteristics. `Itprovides for the demand index (nal steam pressure), a floating controlof high sensitivity superimposed upon a positioning control ofVrelatively low sensitivity. A function ofl the adjustable bleed 4.between the C and D chambers ofthe relay, istosupplement the primarycontrol vof the pressure etective in pipe 4d vwith asecondary control ofthe same or of diierent magnitude as a follow-up or supplemental actionto prevent over-travel and hunting. The relay` 4- 1 is also providedrwith ratio adjusting means .illustrated as ahandknob 43.

4When we speak of ambient pressure or temperature, We, mean the pressureor temperature ambient to. vor adjacent the particular apparatus underdiscussion and within the hull or other confined space in which ,theapparatus is located. It is intended to mean the pressure or temperaturewithin the submarine hull, lairplane body, or other conned spacecontaining the controlling instrumentalities and/,or the controlleddevices. In the present submarine embodiment it `might be termed hullinterior pressure or temperature.

The output signal of relay 41, available in apipe 44, is passed througha hand-automatic selector valve station 45 of thetype described andclaimed in the Fitch Patent 2,202,485 providing a possiblity ofselective remote hand or automatic operation.

The output signal from selector station 45, Whether by automatic meansor hand adjustment, is available in a pipe 46 and acts through thevarious relaysuto adjust the supply rates of the elementsof combustiontosatisfy the demand for steam. Under cruising operationl (light load)vthis is through a control ofthe compressor spillover valve 35 and thefuel oil burner valve S.

The master signal in pipe 46. is subjected upon thee cheese in Steampreseureis.representedby echange in.

leading pressure v'vhiehv turisticas. through relayed?, :41, 4.7 endet.,te vary the degree Qfjthretiiilis QLSpilI-Over valve 35, the resultantychange, in combustion air s upplied to the furnace through conduit 7` ismeasured by an` air ow rate meter 51 and its effect is balancedagainstthe master air pressuresignal.

vThe air ow meter 51 is connected'l-across anorifice 52` located inconduit 7 and actuates the movableelement of .a-pneumatio pilot 53to=therebyil establishdnftha A ehamber.- Qi: a computer;releyfisanairpressure eqn-1.

.anxiously proportional@ the. amount of air, being furnished thefurnace. The output of relay 54, available in a pipe 55, is subjectedupon the A chamber of relay 47 to balance against the master steampressure signal of the B chamber. Thus the relay 47 continuously checksthe master demand for airdlowkagainst the actual measured air ow andprovidesareadjusfting effect upon valve 35 if necessary.

Control o f .fuel o il v supply vrate is accomplished through alcomputenrelay 56vvhich balances the master signal (pipe ,46 to Achamber of relay 56) against a Vsignal' (in B chamber of relay 56)originating from a-fuelioil ow meter 6 previously mentioned.

The meter 6 is sensitive to the pressure differential produced by fueloil flow through an orifice 60 located in oil supply conduit 2; andpositions the movable ele' ment of a pilot 61 thereby establishing inthe B chamber of a ratio standardizing relay 62 an airpressure signalcontinuously representative of fuel oil supply'rate'. 'The outputofrelay 62 vis `subjected upon the B chamber -ofcomputer relay 56 intie-,back opposition or balance to the ymastersteam lpressure signal. Ifthe pressures acting upon the, relay 56 yare not in balance, indicativeofa need foichange yin fuel oil supply rate, the unbalance-isrepresented by va change incontrol pressure inV pipe 63 which actsvthrough asclector station 64 to readjust thev throttling position., ofjfuel oil burner `valves 5v and/or` the Oiipumnsireke mechanism.

In order to provide the possibility of manual adjust,-V mentof-theratioof -fuel vto air flow required, an Aoxidant ratiorelay 67fis installedin thevcontrol circuit for this: purpose. The input pressure to thisrelay, subjected` upon the-relay A chamber from pipe 55, `isproportionall to` combustion air being supplied and byirneansnf aknob-68 adjustment, the ratio ofthe output to .input pressures may beadjusted. The output pressure (in pipe 69;) in-turn acts upon the A*chamberfof relay62 where; it isvr balanced lagainst the Bchamber-pressurev propor. tional to-oil iiovv. The output of relay 62toy computer, relay 56 is thereforeiproportional.to anyy deviation fromthe desired ratiovof oil to combustion oxidant. While the primarychanges von both the combustion air and they oililow are made from thesteam pressurecontroller 3 6, 37, deviationsn the desired proportion offuel-,oilito combustion air are accomplished by variations in thel airpressure signal from the ratiorrelay 62.

During this type of surface operation a hand isolating` valve 78 isclosed and all of the exhaust `products of combustion from the furnaceare discharged over-board by Way of a-pipe 79 through a co-ntrol valve 80.

`Overboard valve 80 is under direct automatic control of controller 8.1ink order to balance the submergence pressure against that of furnace 1to insure continuous f discharge, overboard of the .products ofcombustion-dur- Surface operation-Heaverloads` For operation at greaterthanrcruising loade conditions, the main air compressor 1t) -is used asthe source of -comf bustion air. Control of the' compressor 10 isivaccom-y plished by thefturbneA Athrottle,- valvef-l'insteam condnitg31.The.; master steam pressure,- signal is impressed uma-the: A .chamber of-a- .reiter standardizing; relayr. e

whose output signal (in pipe 73) acts through a selector station 74 inpipe 75 to position the steam throttle 70. Relay 72 serves as an airflow tie-back by having its B chamber loaded from aid flow through abranch 76 of the pipe 55. A change in air pressure signal from themaster selector 45 will cause the main compressor 10 to continuallychange speed in one direction until the air pressure signal from the airilow relay 54 (in pipes 55,

-76) indicates that the required change in combustion air flow rate hasbeen accomplished. During this phase of operation, the compressorspill-over valve 35 remains in a closed position with all changes incombustion air rate being effected by varying the speed of the main aircompressor. The transition from the cruising to the main compressor ismade a semi-manual operation as it occurs rather infrequently and underpreselected desire by the operator. p

During this somewhat heavier load operation the exhause products ofcombustion are utilized by way of expander 11 to provide about 30percent of the power requirements of main compressor 10. vThe handisolating valve 78 is opened and the controller 81 is hand adjusted tomaintain valve 80 normally closed so that all of the products ofcombustion will pass through the expander.

Exhaust gases from the expander 11 leave through a conduit 111 to thesnorkel exhaust (Fig. 3A). Under surface operation the snorkel exhaustfreely passes gases to the atmosphere. Under snorkel operation theintermittent or occasional wave submergence of the snorkel exhaust doesnot introduce suicient back pressure,"rel ative to expander dischargepressure, to disturb or pulsate air supply to conduit 7 from the maincompressor 10.

We have indicated in Fig. 2 that the air flow meter 51 is4 provided withautomatic compensators sensitive to ambient air pressure andtemperature.

Submerged operation During submerged operation it becomes necessary touse oxygen as the oxidant of combustion, and liquid oxygen is vaporized,pressure controlled, and diluted with recirculated products ofcombustion. In addition to providing automatic control of steampressureythe correct fuel-oxidant ratio, and drum liquid level; thesystem maintains the correct ratio of recycled exhaust gases to gaseousoxygen and the desired furnace combustion pressure.

The main compressor is not used and hand isolating valve 78 is closed.Selector station 74 is turned to hand and throttle valve 70 is remotelymanually closed. Selector 74 thereafter isolates valve 70 from pressuresignalsy of pipe 73.

The control of gaseous oxygen flow, through selector station 85 fromsteam pressure and total oxidant is accomplished in the same manner aswhen firing with the main compressor with the exception that the controlsignal in pipe 73 is used to throttle'valve 17.

Gaseous oxygen flow rate is measured by a rate meter 16 arranged toposition the movable element of a pilot 91 thereby establishing in apipe 92 a loading pressure continuously representative of oxygen supply.The computer relay 54, previously sensitive to measured air How, is nowsensitive to measured oxygen ilow (pipe 92) and its output in pipe 55controls the oxygen valve 17 and fuel oil valve 5.

The oxygen ratio relay 90 determines the proportions of recirculated gasmixed with gaseous oxygen to dilute the latter. The input air pressuresignal to the A chamber of relay 90 from pipe 92) is proportional togaseous oxygen flow and the knob adjustment of relay 90 serves as ameans of varying the ratio of the input to the output y ,y pressure in apipe 94 and thus provide selection of the proportions desired. Ameasuring device sensitive to furnace temperature indicates the same 0n,the control gases overboard against the depth of submergence.

panel 112 (Fig. 3A) available to the operator who may adjustthe ratioknob of'relay 90 to regulate the ratio of. recirculated gas owy togaseous oxygen iow and thus maintain furnace temperature below anexcessive value.

Recirculated gas ow through a conduit 21, is regulated by a controlvalve 86 and is measured by a rate meter 87. Meter 87 is arranged toposition the movable element of a pilot 88, establishing in a pipe 89 afluid loading pressure continuously representative of recirculated gasflow rate.

The output pressures from the oxygen'ratio relay 90 and the gas flowcontroller 87, 88 then act through a ratio standardizing relay 96 whichproduces an air loading pressure proportional to deviation from thedesired ratio of gas to 'oxygen ilow, and through selector station 97 toadjust the positioning of recycled gas ow valve 86.

Under this mode of operation, with a portion of the products ofcombustion recirculated to dilute gaseous oxygen and thus limit furnacetemperature, the remainder of the exit gases are discharged overboardthrough valve 80 and pipe 79. Combustion chamber pressure must bemaintained sufliciently high to discharge the Oxygen gaseous supply isused to aspirate the recycled gas to the furnace. Combustion pressurecontrol is accomplished by throttling valve 80 in overboard conduit 79.

Both themain compressor and the cruising compressor have characteristicssuch that flow and pressure rise and fall together. When it is desiredto transfer from air burning (particularly from the main compressor) to`oxygen tiring, it will be seen that, as we begin to open oxygen valve 17through hand manipulation of selector station 85, the oxygen flow meter16 will act through pipe 92, relay 54, pipe 76 and relay 72 to indicatean excess of oxidant and tend to cut back on valve 70. To prevent thisand maintain combustion chamber pressure, we tie the output of selectorto relay 48 (through pipe 99) which controls the spill-over valve 35 ltodump air without changing compressor speed.

For all three modes of operation the feed water control supplies theboiler in accordance with load demand. This is accomplished by meteringsuperheated steam ilo-w in the outlet header 32 with flow rate meter 33and feed water inflow rate through conduit 23 by flow meter 27. Airpressures proportional to steam outflow and water inow are developed bythese measuring controllers, and through a relay develop an air pressurewhich positions the vfeed water control valve 26 to maintain the samerate of water inow to the boiler as steam ow therefrom. Deviations inseparator drum (22) water level are sensed by measuring controller (28which develops an air pressure proportional to water level and acts uponthe relay to modifyvthe steam flow-water flow control of valve 26 asnecessary to maintain the correct separator drum level. During rapidload swings, excessively high dmm levels are prevented by opening thedrum spill-over valve 113 by the air pressure developed by controller28.

Snorkel operation When firing the unit under snorkel conditions, changesin ambient pressure within the hull are expected although the depth ofsubmergence is relatively constant.

The ambient pressure cut-back relay 39 has been included main.Yair'icompressor, .vv-hem the airtforfcombustongis: drawn,from,thet-hullainterior. t Were ;the firing. rate "not reduced( and the`-air withdrawalV ffrtom' the hull :undiminr ished) during snorkelclosure of some 8 seconds-fthel hulltairl; woulde be ,exhausted .tofsuchV anrextent' fas. to `-be dangerous tothex personnel; Additionally;Ila trip j switch 114 y-measuring hull -pressure has. been. included \forfthe 1 purpose :ofttt'ippingg out. the -:lires byjvalve lsrfuponreaching a dangerously low .'hull pressure;

Referring specically to Fig. 2, relays 41', 72, 47, 62 and `96 :havebeen designated asvv standardizing I.type relays. PorVV use underambient-pressure-changing.= Icon ditions, such Aas .might beyencountered-'during snorkel'- operation, or even ,under varying :depth-r'of submergence, itwas found'thatf-thisfrelay Wouldrtendtovhold aconstant absolute .pressure `.following-a isuddcnzchangerather'; than 'aconstant 'gagezrpressure :which :is Jrequireditoffthe system, andvwhichthewremainderjof the= componentsv produce.v To compensate forfthis, aniadditionalsbellows was; added, together with ,ableedVvalvermwhichil would compensate forr the Vreset'rate bleed adjustmentin such:- away that the outputduring'variablerambient pressureLconditions e will remain on a constant gage lpressure basis.` Detailslof thiscompensation Wasnotlshown2in1l the present i drawing- 'and treference should. beffnad tothe copending'application ofv Howard C..Sohink, ySerial,v No.-318,308, filed November '1, 1952, nowPatent,12,860,- 650-whichf is directed particularly to such. anfarnbientpressure or -barometric pressure compensated-"relay It will be seen thatwe -have providedfapparatusiandi a-methodfof operation g to handle a;steamv .boileiilplantt for-a. submarine which. willfunotionfunder threedefinite phasesl of operation; surface; snorkel andzsubmerged.`Theirsttwo conditions of operation take ainr from athe :hull interior'by way of either acruising or' maini compressor; depending uponA loadrequirements. Duringifsubmerged' operation, liquid oxygen lis"evaporated andfsupplied lto theV boiler furnace in lgaseouszform.Regardless -of fthe method of operation,- the 1automatic :combustion.'Lcontrol:

performs the following basic functions; maintaining steam pressure t.at: the :correct -value, ,maintaining combustion pressure, maintainingthe correct ratio`of fuel tolvoxida'nt,v and".v maintaining feed' wa'tersupplyirate. asneededi. Change-over from one-.method`offfirirrgsto.anothertis manuale-,through remotelyk actuated'`instrumentalitie's and immediately following lsuch change-over,theautomatic control system' functions under the new mode of operation.

Whilewe havedescribed certain' automatic methods and systems of`operationpunder diierent'conditions.of service, it will beapparent. thatourl methods imayl be manually performed'through iobservation'of thevarious. measuring instrumentalitie's` and remote manual controli'of the.controllablefactors In Fig. BAW/e show'vaI central' con-trol panel 112:upon which Ymay'bemountedtvarious measuring'devic'esoit-variables inthe operation. ofzthe plant,'for.example, meters 36,151; 16,6, 37,31,33, 28,127. etapas-'well as manualfautomatic selector-,stations 45;v74,j 85, 49, 64, 97, and 125, Some, or all of the relays may also bemounted on the panel 112, as well as controllers 101 and 114. Theoperator may observe .the measuring instrumentalities' and remotelymanuallyoperate the selectorstations to perform the claimedmethods'.

It'will be evident that, while` we have chosen to illus-- trate anddescribe one preferred embodiment of our invert-z tionin connectionwithla submarine as exempli'f'ying an enclosed'space, wel contemplatethat our invention is equallyf-as well adapted't-o enclosed spacesas,for 'example, the 'pressurized hulls of airplanes, the pressurizedlor"evacuated containersV of 1auto-maticpiles,v or the like.

What we claim as new, and'desire to secure 'by'L'etters Patent oftheUnited States-is:

l. The method 'of operatingn4 the steaml generating processv of asubmarine propulsion unit having apressurized combustion'furnacesupplied 'a iluentfuel and fluid: oxidant including, supplying theoxidant from the submarinei-nterionn controllingthe fuel antioxidantsupplya rate '.toesatisfy steam :demand 'ruponethe vrunitydischargin Lthe products :of 'combustion to,v the: submarine texterionrby?maintainingithe pressurel within 'the .furnace Substantially@constantande-suticiently high to maintain-discharge'.fronr;thef-furnaceat variousdepths ofsubrnergence;andlimi'ting1the1ftrnacefuel and 'oxidant supply 4Jfrorn'thefai'rpressuref within thesubmarine.

2.-The method; offclaim- 1 whereiny thenair is the-com-- bustion oxidantwithdrawn from' thesubmarine interior at: -a relatively-'constante rate:and vany-excess air .-is confV tinua-lly; returned tto. the .submarineinterior.

3. A systemfor controlling the steam generation; processl of-,a\submarinepropulsion; unit subject -to sur,- face.snorkel -andsubmerged.- operating conditions-ina cluding in combination, a steamgenerating furnace f com.-` bustiongchamber in thefsubmarineinter-ior.,a-fuelfsupply conduit-fior the-furnace,-an-.oxidant-supply;conduit'tfor'i theffurnaceya rstmeter forfthe fuelconduit,` afsecondt.

meter for the A oxidant conduit, regulating valves fin eachv offtheconduits; amaster fsteam` pressure controller posi.- tioning'theconduitY valves simultaneously; a ratio. deter mining means .lsensitives to the-rstand. second meters modifying the regulation of thefuel supply conduityalve,

aw constant supply :of `fuel -for the `fuel supply conduitoftheturnace,` ,a compressor oftconstantflspeedfy connectedl` totheoxidant. supplyV conduit for supplying@ air ffrom' the submarineinterior,` .andta valve y'i112 the oxidant conduit l between thecompressonand furnace'under the-conjoint control of `the master steam--pressure controller'and .ther oxidant. meter.- f

4.- `The combination. of 'claim 3 in lwhichnthecom-f pressor is drivenby a steam turbine and gas expander@ andcthere` is fincluded, a ductIforfconveyiligithe :gaseous products of combustion from' the-furnace`to .the-expander; a control valve for the steam duct coming V'to-theturbine,l

and means sensitive .to the master steam-pressure controller and theoxidant 'meter "toconjointly position the control' valve.

5.A Theccombinationrof c1airn:4 lwherein meansrespon-w sive .totheinterior lair pressure of the-submarineopposesf thetsmaster steamapressurecontroller tondecrease :the-

. rate of'fuelandoxidant` supply .when theinterior airpres-.

` supply conduit is connected to a source `of oxygen. andf thereisincluded invthecombination; a'meterffor-irthe oxygeni in f; the oxidantisupply f conduit, afvalve` inuthe oxidant. supply conduitpositioned'byrthe master steam: pressure controller fand* the: oxygen meter;y and asystem=v for mixing with .the 'oxygen'. a portion of the'produc'ts'zof`combustion. l

8;. Thef'combination ofv claim7 in whichythe'mixing` i systemfincludestaconduit from=fthe"furnace :exhaust tov the-furnace burners, a meter for:the products "of 6Com-, busti'onainthe conduit; andva'valve'in theconduitv for the' products-.of combustion.positioned;bythey oxygen-meterandthe Vproducts of Acombustion meter.l

References- Cited in the lileofthis patent4 UNITED STATES PATENTS1,126,6161 Cage' Jan. 26,;r 19I5 1,345,757' Emmet.l Julyff, 19201,380,304v Norton May`31, 1921 1,695,472 Roucka .1. De :..18,` 19281,721,800 Wunsch July' 23',LV 1929' Beslerlv Iulyl; 1941 (Gtherreferences on following page) 9 UNITED STATES PATENTS Rasor July 14,1942 Roberston June 15, 1943 Holthouse May 14, 1946 McCracken Dec. 17,1946 Fellows Aug. 15, 1950 Dickey Dec. 30, 1952 Bristol June 1, 1954 10Bristol June 15, 1954 Hoke Oct. 18, 1955 FOREIGN PATENTS Great BritainApr. 19, 1917 Great Britain July 24, 1946 OTHER REFERENCES

